McLoughlin was speaking after he and Mayor Boris Johnson announced plans to hand control of inner suburban routes to Transport for London.

The minister and Mr Johnson staged a joint press conference at Liverpool Street station earlier on Thursday which was later followed by a separate photo-call alongside Tory candidate Zac Goldsmith.

Previous mayoral contests featured a host of established figures including Ken Livingstone, Frank Dobson, Steve Norris, Simon Hughes and Mr Johnson, all of whom were well known to Londoners.

However this year’s frontrunners are far less familiar faces, a disadvantage the Tories are seeking to overcome by positioning Mr Goldsmith as someone who has managed to deliver for London during the campaign.

Mr Goldsmith’s mayoral campaign claim their candidate has been “been working with the Department for Transport to secure the devolution of further rail franchises to Transport for London” and point to a letter dated last November as evidence of his efforts.

TfL’s work to convince ministers to devolve more of London’s rail services has been underway for most of Boris Johnson’s second term and has been endorsed by all parties on the London Assembly as well as senior Labour figures, including former Transport Secretary Lord Adonis, and business groups.

“That’s why I’ve been campaigning for some time for the Mayor to take control of who runs London’s commuter routes and insist on a better service for passengers.”

However McLoughlin has since claimed that Khan “has shown no interest in engaging with ministers on devolving rail services” while Goldsmith says his rival “made no attempt to make this happen, has made no attempt to talk to Ministers about this as an MP or mayoral candidate”.

Both men also point out that Mr Khan failed to devolve any rail services during his time as Transport minister, a post the Labour candidate has repeatedly referred to in order to establish his own credentials with voters.

Asked to comment, a spokesperson for Mr Khan said: “The Tories are desperately trying to deflect attention from the fact they have no interest in stopping strikes – and that they treat the millions of Londoners simply trying to get to work with total disdain.

“The facts show there were more twice as many Tube strike days with Boris Johnson in City Hall than there were under Ken Livingstone.”